The assembly of an aircraft engine is the last procedure during manufacturing of the aircraft engine, and is also one of the most important manufacturing procedures. According to the current condition of designs and processing technology of the aircraft engine, the quality and efficiency of the assembly work have great influence on the quality, performance and production efficiency of the engine. Therefore, coaxiability of the mounted rotors needs to be improved as much as possible during the assembly, so as to further reduce the vibration of the aircraft engine and improve the performance of the aircraft engine. However, the aircraft engines are assembled completely by hand in the actual production, the assembly accuracy and assembly stability depend entirely on the operational experience and technical skills of the workers, Therefore there is a need for a rapid and effective method that is capable of guiding the assembly of the rotors of the aircraft engine so as to increase the assembly efficiency, reduce vibration of the aircraft engine and improve the performance of the aircraft engine.
In recent years, the aircraft engine assembly test technology has attracted more and more attention, and becomes the focus of aircraft engine researches. More and more researchers have been making deep researches on rotors of the aircraft engine. For example, ROLLS-ROYCE PLC proposed a solution (System and method for improving the damage tolerance of a rotor assembly; European Patent Publication No. EP2525049A2), which mainly comprises the steps of obtaining stress signals at each position of the rotor by each sub-system, analyzing the signals collected by each sub-system by a main system, and then analyzing the influence on the assembly from the damage tolerance parameters of each rotors, thereby improving assembly of the rotors of the aircraft engine. Yet, the problem of this method lies in that: it does not analyze the influence on the assembly in terms of the geometric quantities of the rotors, and thus cannot improve the impact of geometric quantities on the assembling.
XI'AN JIAOTONG UNIVERSITY proposed a method for testing the assembling performance of the rotors of the aircraft engine (Method for testing assembling performance of rotor of aircraft engine, Publication No.: CN101799354A). The method can comprise the steps of: firstly exciting a rotor of an aircraft engine to vibrate by means of a vibration exciter; obtaining a multicarrier-coupled impulse response signal of the rotor of the aircraft engine with a vibrating sensor and a signal-acquiring system software; analyzing the obtained multicarrier-coupled impulse response signal of the rotor of the aircraft engine by means of a dual-tree complex wavelet transform, so as to obtain eight single-carrier impulse response signals of the rotor of the aircraft engine; and finally getting the average assembly performance index of the obtained eight single-carrier impulse response signals of the rotor of the aircraft engine, wherein the assembly performance of the rotor of the aircraft engine is determined to be qualified if the average assembly performance index obtained is larger than or equal to 10, and the assembly performance of the rotor of the aircraft engine is determined to be unqualified if the average assembly performance index obtained is less than 10, and the rotor needs to be reprocessed and repaired. The problem of this method lies in that there is no guidance for assembling the rotor of the aircraft engine.
LUOXIN PRECISION PART (SHANGHAI) CO., LTD. proposed a coaxiality measuring device (A Coaxiality Measuring device, Publication No.: CN202024752U). The device comprises a pair of driving spindles, which are arranged on a main body of the instrument and are synchronously controlled by a synchronous mechanism to rotate; a probe and positioning datum planes are respectively and correspondingly arranged at the inner ends of the driving spindles; and a sensor probe is arranged above the position between the probes. It mainly solves the problem on the coaxiality and vibration of precision parts in the prior art. Yet, the detect of this method lies in that it only measures the coaxiality of the measured part, but this to solve the problem of poor coaxiality of the rotors after assembling.
SHENYANG LIMING AERO-ENGINE (GROUP) CO. LTD. proposed a gap measurement method (A non-contact measurement method for the radial gap of the engine rotor blade tips, Publication No. CN102175135A). The method adopts capacitance measurement techniques and comprises the steps of: assembling the measurement system, calibrating the sensor and determining the relationship between the radial gap of the blade tips and the voltage, fixing the sensor on the blade; and measuring the radial gap of the blade tips of the engine rotor. The problem of this method lies in that it does not take the influence of the axial mounting surface on the assembled rotor during the assembly of rotor into account.
The test objects of the assembly of the aircraft engine are stators and rotors of a turbine. In the condition that the processing precision of the parts meets the requirements, the final test result is determined by the fitting state after installation, and the assessment index is mainly the coaxiality parameter of the assembled rotor. Rotation of the engine can produce high pressure, and the rotor of the engine is composed of a plurality of separate parts which are combined together, it is ideal that a rotatory shaft of each part overlaps with an axis of the whole engine. In operation, the high-performance engine has a high speed of rotation of greater than 10000 rpm, so the axial or radial deflection of the single member will inevitably result in deviation of a center of a turbine disk from the rotation axis of the engine. In such a case, a huge centrifugal force will be produced, causing unbalanced rotation of the rotor and vibration of the engine. Therefore, it is important and difficult to guarantee the coaxiality of each part after assembling.
For a model assembly where a coaxiality optimization method is not adopted, there are errors of jitter, eccentricity, inclination in the axial and radial direction of each part due to the limitation of processing precision. If the assembly is performed directly and randomly, a case where a “banana”-like bending is formed may occur. In other words, the upper parts have been accumulated with the eccentricity or inclination error of the lower parts, resulting in great deflection and inclination of the whole model after being assembled, further causing poor coaxiality of the rotor of the engine, and thus it is hard to meet the requirements for use.
At present, the traditional assembly methods are still adopted in the domestic engine assembly, which mainly conducts measurement manually with a dial gauge, wherein the engine is assembled in an order from bottom to top, and measurement is conducted after assembly of each part, so as to ensure that the whole body can meet the threshold value of coaxiality every time after a part is added; and then another part is mounted upwardly. Each new part is mounted by using the previous part as a reference, and the final coaxiality of the whole body is required to be within a certain range. Such a method is time consuming and is very likely to need reprocessing, significantly affecting the mounting efficiency and the success rate of one-time mounting; a successful assembly usually takes 4 to 5 days. Moreover, since the location is not the optimal assembly position, 4 to 5 times of disassembly is usually required. Plus, workers have to conduct assembly based on their experiences, and each assembly needs to go through hot processing and cold processing. Therefore, the current methods for assembling an aircraft engine are low in mounting efficiency, difficult in mounting and poor in coaxiality after assembly, which affects the performance of the engine.